Question

You are dining at your favorite restaurant and eating your favorite meal when you start to think about the digestion process (sorry to ruin your meal). Briefly explain this process when food enters your stomach then in your small intestine. Include the following terms/structures in your explanation: stomach; chyme; hydrochloric acid; 3 basic tasks of stomach; length of time in stomach; 3 structural parts of small intestine; describe what happens in the first 25 centimeters of the small intestine; role of pancreas & gallbladder; bile; bicarbonate ions; peristalsis & segmentation; composition of chyme in small intestine.

Answer 1

The digestive system is a collective name used to describe the alimentary canal its it's accessory organ and a variety of digestive process that take place at different levels in the canal to prepare food eaten in the diet for absorption.

The elementary Canal begins at the mouth passes through the thorax abdominal and pelvis and ends at the anus.

It has a General structure which is modified at different levels to provide further processing occur at each level. The digestive process gradually break down the food eaten until they are in a form suitable for absorption. When the food is taken by mouth it is too complex to be observed from the elementary canal. Digestion Digestion release it constituents: amino acid mineral salt fat and vitamins. Digestive enzymes that affect these changes are secreted into the canal by specific glands some of which are in the walls of the canal and some outside the canal but with duts leading into it.

After absorption nutrients are used to synthesise body constitution they they provide the raw materials for the manufacture of new cells hormones and enzymes and the energy needed for this and other process and and for disposal of waste materials.

The activities in the digestive system can be grouped under five main headings:

INGESTION: this is the taking of food into the alimentary canal

PROPULSION: this mixes and most the contents along the alimentary track.

DIGESTION: this consists of. Mechanical breakdown of food

Chemical digestion of food

ADSORPTION: this is the process by which digested food substances passes through the walls of some organs of alimentary canal into the blood and lymph capillaries for the circulation and used by body cells

ELIMINATION: food substances that have been eaten but cannot be digested and absorbed or exited from the elementary Canal as faeces by the process of defecation

ORGANSOF THE DIGESTIVE SYSTEM

Mouth

Pharynx

Oesophagus

Stomach

Small intestine

Large intestine

Rectum &

Anus.

ACCESSORY ORGANS OF THE DIGESTIVE SYSTEM various sections are poured into the elementary track through the ways .: Inside the track:eg. Gastric juice

Outside the track:eg. Three pairs of salivary glands,

Panvreas, and bile duct.

STOMACH:

The stomach is a j shaped dilated portion of the alimentary track situated in the epigastric umbilical and left hypochondriac regions of the abdomen cavity.

STRUCTURE OF THE STOMACH:

The stomach is continuous with the oesophagus at the cardiac sphincter and with the duodenum at the pyloric sphincter.

It has to curve curvatures

The lesser curvature: it is short life on the posterior surface of the stomach and and is downward continuation of the posterior wall of the oesophagus. Just before the pyloric sphincter IT compared to complete the J shaped.

The greater curvature: the oesophagus join the stomach anterior region angle acutely upwards curves downvids and and then slightly upwards towards the pyloric sphincter.

PARTS OF THE STOMACH

The fundus.

The body and

The pylorus.; At the distal end of pylorus is the pyloric sphincter guarding the opening between the stomach and duodenum. When the stomach is inactive the pyloric sphincter is relaxed and open. When the stomach contains food the springtime is closed.

WALLS OF THE STOMACH:

The four layer of tissue that comprise the basic structure of the of the alimentary canal are found in the stomach but with some modifications:

This consists of three layers of smooth muscle fibers.

An outer layer of longitudinal fibres

Middle layer of circular fibres

An inner layer of oblique fibers.

MUCOSA: (rugae) when does stomach is empty the mucous membrane cleaning is thrown into longitudinal Folds called rugae.

GASTRIC JUICE AND FUNCTIONS OF STOMACH.

Stomach size varies with the volume of food it contains which male have been eaten the food accumulates in the stomach in layers, the last part of the mail remaining in the fundus for some time. Mixing with gastric juices takes place gradually and it maybe sometime before the food is sufficiently acidified to stop the action of salivary amylase.

The activity of gastric muscle consists of churning movement that breaks down the bolus hand mixers it with gastric juice and peristaltic wave that proper in the stomach contents towards the pylorus.

When the stomach is active the pyloric sphincter closes. Strong peristaltic contraction of pyloric Forces chyme, gastric contents after they are sufficiently liquefied, through the pyloric sphincter into the duodenum in small spurts.

Functions of gastric juice:

Hydrochloric acid: acidified the food

Pepsinogen: activated to pepsin by hydrochloric acid

Intrinsic fqctor: it is necessary for the absorption of vitamin B12 from the ileum.

SECRETION OF GASTRIC JUICE:

Succession reaches its maximum level about 1 hour after a meal then declines to the fasting level after about 4 hours.

SMALL INTESTINE:

The small intestine is continuous with the stomach at the pyloric sphincter. It is about 5 metres long.

PARTS OF SMALL INTESTINE.

Duodenum :

Jejunum

The ileum.

DUODENUM: the duedenum is about 25 CM long. Secretions from gallbladder and pancreas is it in some common structure, hepatopancreatic ampulla-and enter the duodenum

m at the duodenal papilla. It is guarded by a ring

Of smooth muscle, the hepatopancreatic spinster.

STRUCTURE OF SMALL INTESTINE

The walls of the small intestine are composed of 4 layers of tissue.

PERITONIUM MESENTRY: 899 which attaches the jejunum and ileum to the posterior abdominal wall.

MUCOSA: the surface area of small intestine mucosa is greatly increased by permanent circular Folds,villi microvilli.

PERMANENT CIRCULAR FOLDS: Unlike the Rookie of the stomach are not smooth out when the small intestine is distended. They promote mixing of time as it passes along.

VILLI: these are tiny finger like projection of mucosal layer into the intestinal luman , about 0.5 to 1 mm long.

MICROVILLI: tables consists of column epithelial cells or enterocytes with tiny micrivilli 1um long.

Along with these Goblet cells and lactels are present.

ROLE OF PANCREAS.

The pancreas this is a pale great Gland weighing about 60 grams.. itit is about 12-15 cm long.

It has has head, body, and tail.

The pancreas this is both an exocrine gland and endocrine gland.

The exocrine pancreas :

Consists of large number of lobules, which are made of small acini ( secretory glands ).

Is Loreal trained by a tiny doctor unite to farm pancreatic duct. Which extend the whole length of Gland.

The endocrine pancreas:

Groups of specialised cells called the pancreatic islets of langerhans. The endocrine pancreases secrets hormones insulin and glucagon.

GALLBLADDER

The gallbladder Isa pear shaped sacsac attac to the posterior surface of the liver by connective tissue. It act as a reservoir .